Publicaciones: Sistemas Hibridos Nanoestructurados

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03

Dec 2018

Crystalline Structure and Vacancy Ordering across a Surface Phase Transition in Sn/Cu(001)

Posted by / in Publicaciones 2018, Publicaciones: Sistemas Hibridos Nanoestructurados, Publications Nanostructured Hybrid Systems 2018, Últimas Publicaciones CINN / No comments yet

We report a surface X-ray diffraction study of the crystalline structure changes and critical behavior across the (3√2 × √2)R45° → (√2 × √2)R45° surface phase transition at 360 K for 0.5 monolayers of Sn on Cu(100). The phase transition is of the order–disorder type and is due to the disordering of the Cu atomic vacancies present in the low temperature phase. Two different atomic sites for Sn atoms, characterized by two different heights, are maintained across the surface phase transition.

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03

Sep 2018

Magnetic order and disorder in nanomagnets probed by superconducting vortices

Posted by / in Publicaciones 2018, Publicaciones: Sistemas Hibridos Nanoestructurados, Publications Nanostructured Hybrid Systems 2018, Últimas Publicaciones CINN / No comments yet

We have studied two nanomagnet systems with strong (Co/Pd multilayers) and weak (NdCo alloy films) stray magnetic fields by probing the out-of-plane magnetic states with superconducting vortices. The hybrid samples are made of array of nanomagnets embedded in superconducting Nb thin films. The vortex motion detects relevant magnetic state features, since superconducting vortices are able to discriminate between different magnetic stray field strengths and directions. The usual matching effect between the superconducting vortex lattice and the periodic pinning array can be quenched by means of disorder magnetic potentials with strong stray fields at random. Ordered stray fields retrieve the matching effect and yield asymmetry and shift in the vortex dissipation signal. Furthermore vortices can discriminate the sizes of the nanomagnet magnetic domains, detecting magnetic domain sizes as small as 70 nm. In addition, we observe that the vortex cores play the crucial role instead of the supercurrents around the vortex.

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03

Aug 2018

Cycloidal Domains in the Magnetization Reversal Process of Ni80Fe20/Nd16Co84/Gd12Co88 Trilayers

Posted by / in Publicaciones 2018, Publicaciones Destacadas, Publicaciones: Sistemas Hibridos Nanoestructurados, Publications Nanostructured Hybrid Systems 2018, Últimas Publicaciones CINN / No comments yet

The mag netization reversal of each individual layer in magnetic trilayers (permalloy/NdCo/GdCo) is investigated in detail with x-ray microscopy and micromagnetic calculations. Two sequential inversion mechanisms are identified. First, magnetic vortex-antivortex pairs move along the field direction while inverting the magnetization of magnetic stripes until they are pinned by defects. The vortex-antivortex displacements are reversible within a field interval which allows their controlled motion. Second, as the reversed magnetic field increases, cycloidal domains appear in the permalloy layer as a consequence of the dissociation of vortex-antivortex pairs due to pinning. The field range where magnetic vortices and antivortices are effectively guided by the stripe pattern is of the order of tens of mT for the NiFelayer, as estimated from the stability of cycloid domains in the sample.

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